The present invention relates to a mass analyzer and an operation method thereof.
An apparatus that simply measures a minute amount of substance contained in a mixed sample with high sensitivity extemporarily is demanded during measurement of a pollution of soil or air, agricultural chemicals inspection of foods, or diagnosis using metabolites in blood. As one of the methods capable of measuring a minute amount of substance with high sensitivity, a mass spectrometry is used.
In the mass spectrometry, substances are decomposed into ions of a vapor phase in an ion source, and they are introduced into a vacuum part to perform a mass separation. For performing the mass spectrometry with high sensitivity, an improvement in the sensitivity based on an improvement in performance of an ion source is important in addition to a modification of a mass analyzer part or detector.
Some of the ion sources applicable to a sample that is solid phase extracted from a solid or liquid sample, or a liquid or gas sample are known.
An old-traditionally used method is an electron impact ionization. This is a way in which a sample is vaporized by heat to become a sample gas and an electron beam is irradiated onto the sample gas under vacuum for ionization. Since high energy is used in the electron impact ionization, fragmentation in which a sample molecular structure is broken is easy to occur. The electron impact ionization is used for estimating an unknown sample from a spectrum pattern.
As an ionization method in which the fragmentation is small, an atmospheric pressure chemical ionization is used (U.S. Pat. No. 7,064,320). This is a way in which a sample is vaporized by heat to become a sample gas, and it is mixed with reagent ions generated by corona discharge under atmospheric pressure and ionized by an ion molecular reaction. Further, as a method having ionization efficiency higher than that of the atmospheric pressure chemical ionization, a dielectric barrier discharge ionization is known recently (WO 2009/102766). In the dielectric barrier discharge ionization, dielectric is sandwiched between electrodes so that a temperature of neutral gas or ions in plasma can be prevented from rising up and plasma with a low temperature can be generated. Excited molecules or ions are generated by the plasma and reacted with a sample gas, and sample ions are generated. A large amount of excited molecules or ions are generated in the dielectric barrier discharge, and the ionization efficiency is high. In WO 2009/102766, plasma ejected from a probe in an atmospheric air is directly applied to samples to be ionized and the generated ions are introduced into a mass analyzer.
As an ionization method in which the fragmentation is small and a sample fails to be heated, an electrospray ionization is used (U.S. Pat. No. 5,306,412). This is a way in which an electrolyte solution containing samples is sprayed under atmospheric pressure while applying a high voltage to that solution to thereby ionize them. Further, the above-described ionization method also includes a matrix assisted laser ionization (WO 2007/097023). This is a way in which laser light is irradiated onto a sample mixed with a matrix chemical under vacuum and the sample is ionized.